Slight irregularities on the wafer surface—or on deposited films—can distort semiconductor patterns as they are transferred by a lithographic process to the wafer. Chemical mechanical polishing or planarization (CMP) has become the process of choice for preventing this distortion by first planarizing the wafer surface to a flat, uniform finish.
To planarize the wafer, CMP systems use an abrasive suspended in chemical slurry that levels wafer topography during mechanical polishing. In a common configuration, the wafer is held by a spinning pressure ring against a polishing pad that is held on a spinning platen.